The overall objective is to determine and define the microflora of various stages and states of peridontal diseases in man, and to detemine the etiologic agents. Specifically in this proposal, toward the overall objective, the aims are 1) to determine the accuracy and repeatibility of sampling and to estimate the magnitude of the various components of variability, 2) to determine and define the microflora of experimental gingivitis in children and compare the flora with that of young adults previously studied using the same model, and 3) to determine and define the microflora of naturally occurring gingivitis in children and adults. Samples will be obtained from human subjects whose periodontal status meets the criteria for study within the objectives and is documented by clinical measurements and indices. Samples are anaerobically dispersed, inoculated and cultivated in roll tubes and blood agar plates for maximum non-selective growth of bacteria, including spirochetes. Randomly selected colonies are characterized to the species- or subspecies level using polyacrylamide gel electrophoresis, 35-36 test media for biochemical reactions, gas-liquid chromatography of end products and serology. Strains are identified by comparison of characteristics with the type strain of the species and other reference strains. Sample-to-samples variation and relative magnitudes of other components of variation (site-to-site, time-to-time, person-to-person, effect of sampling) will be determined from duplicate samples at 3-week intervals. The flora of 5-7 yr-old children will be assessed at days 4, 11 and 26 of no oral hygiene and at a subsequent time if needed for the development of gingivitis. The flora of naturally occurring gingivitis will be evaluated in samples from inflamed sites in children 5-7 years of age and in 18-30 yr-old adults.